Electric relay



Nov. 20, 1951 HUFNAGEL 2,575,312

ELECTRIC RELAY Filed Aug. 19, 1949 "if? 5 q :2 I9 21 lnsaladalz. 50a 5052 I0 20 2 Fyi.

IN VEN TOR.

H15 ATTORAZ'Y Patented Nov. 20, 1951 UNITED STATES PATENT OFFICEELECTRIC RELAY Andrew Hufnagei, Penn Township, llegheny County, Pa.,assigncr to Westinghouse Air Brake Company, a corporation ofPennsylvania Application August 19, 1949, Serial No. 111,209

4 Claims. 1

My invention relates to electric relays, and particularly to relays of atype commonly employed in certain railway signaling systems and termedcode detecting relays.

it is common in certainr'ailwa'y signaling sys tems to use electriccircuits which are periodically interrupted or coded. This coding actionmay take place at one of several different freduencies, depending uponthe intelligence to be transmittedoiier the circuits. Such circuitscommonly supply current to a code following relay which picks up itscontacts when each current impulse received and drops its contactsbetween the current impulses. It is desirable for safety reasons tocheck the operation of such code following relays to ascertain that therelay is following code and that its front and back contacts are openingand closing properly. Several such code detecting arrangements have beenproposed in the past. See, for example, Letters Patent or the UnitedStates No. 2,320,748, issued to George R. Pfla'sterer on June 1 1943,entitled Railway Signaling Apparatus.

It is an object of my invention to provide an improved and simplied codedetecting relay of the type described. 7

' I carry out the foregoing and other objects of my invention byproviding a closed magnetic circuit and a magnetic circuit with air gapshaving a common element with the closed circuit for my code detectingrelay. The closed magnetic circuit comprises a closed loop of magneticmaterial having two electric windings so connected respectively to thefront and back contacts of the code following relay that they areeffective when energized to create opposing magnetic fluxes in the loop.A shading coil is placed on a portion of the loop to delay the buildingup and decaying of magnetic flux through that loop portion. The secondmagnetic circuit provided forms a magnetic shunt around the shading coilporti'or i of "the loop. This branch magnetic circ'uit includes anarmature and at least one pole structure toward which the armature is attimes attracted. The branch circuit includes air gaps between its endsand the closed loop so that its reluctance is much greater than that oftheloop during steady magnetic conditions in the loop. The polestructure includes two magnetically parallel portions and a secondshading coil on one of said portions. The second shading coil isefiective to retain the armature in its attracted in its attractedposition when and only when the windings are alternately energized at afrequency within a predetermined range. In other words, the armature isattracted only when the code following relay is following code and itscontacts are functioning properly.

I shall describe two forms of electric relays embodying my invention,and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a schematic view of an electricrelay embodying my invention and an energizing circuit for that relay.Fig. 2 is a side elevational view of the relay shown schematically inFig. 1. Fig. 3 is a schematic view of another form of relay embodying myinvention.

FIG. 1

There is shown in this figure a code transmitter relay CT having acontact which controls the energizing circuit of a code following relayRelay CF is in turn provided with a contact which controls energizingcircuits for a code detecting relay embodying my invention and generallyindicated by the reference numeral I.

The code detecting relay l is provided with a magnetic circuit whichincludes a loop 2, which in the example shown takes the form of a hollowrectangle. A pair of electric windings 3 and 4 is provided on oppositesides of the loop 2. Wind ing 3 may be energized over an obvious circuitcontrolled by the back contact of relay and winding 4 may be energizedby another obvious circuit controlled by the front contact of relay CF.The windings 3 and 4 are shunted by are suppressing resistances 5 and 6,respectively.

One side 2a of the loop 2 carries a heavy shading coil or ring I, whichis effective to delay the building up or decay of magnetic flux throughthe part of the magnetic circuit which it en'- circles.

A branch magnetic circuit is provided, which is magnetically in parallelwith the loop portion 2a encircled by the shading coil 1. This branchmagnetic circuit includes two pole structures 8 and 9 and an armatureIll. The pole structures 8 and 9 are separated from the opposite ends ofthe loop portion 20. by air gaps II and 12. The reluctance of the branchmagnetic circuit, including the air gaps H and I2, is so related to thereluctance of the loop portion 20. that very little flux flows throughthe branch magnetic circuit during steady magnetic conditions in theloop 2. However, during transient magnetic .con ditions in the loop 2,such as occur during alter- -.nate energization of the windings 3 and '4when Each of the pole structures 8 and 9 is provided with twomagnetically parallel portions, such as M and 8b, and the correspondingportions 9a and 9b. The portions 8a and 9a of the pole structures 8 and9 are provided with shading rings or coils I4, which are efiective todelay the building up and decay of magnetic flux in their respectivepole portion.

The shading coils I4 are effective to maintain the magnetic flux duringthe time when both coils 3 and 4'are deenergized, due to the passage ofthe contacts of code following relay CF between its front and backcontacts, and are thuseifective to retain the armature I in itsattracted position at such times.

Operation The operation of the relay I when the relay CF is followingcode is believed to be suificiently described above. We will now proceedto consider the operation of relay I when the relay CF is not followingcode, and then its operation during various types of malfunctioning ofthe contacts of relay CF.

First let it be assumed that relay CF is not following code, but iscontinuously deenergized or continuously energized. In either event, thefront or the back contact of relay CF is continuously closed, and one ofthe windings 3 and 4 is continuously energized. This produces a steadymagnetic condition in the loop 2. After this condition has persisted fora short time, the flux delaying effect of the shading coil 7 isovercome.

and the portion 2a of the loop 2 then effectively shunts the magneticflux away from the branch magnetic circuit including the pole structures8 and 9 and armature I0. Armature Ill is then no longer attracted to thepole pieces 8 and 9 and therefore drops to its deenergized position.

Let it now be considered that relay CF is following code, but that oneof the stationary contacts sticks against the movable contacts so-thatonelof the windings 3 or 4 is continuously energized while the other isintermittently energized. When both windings 3 and 4 are energized, theytend to buck each other in the loop 2 and in the branch magnetic circuitand are hence then effective to prevent attraction of the armature Ill.During the intervening period, the one winding which is energizedcontinuously is eilective to send flux through the loop 2. Although thisflux may be intermittently bucked down by the other winding, thedirection of flow of flux through the loop is never reverse under theseconditions, and hence the continuously energized winding is graduallyeffective to build up a flow of fiux through the loop portion 2a. Thisflux is shunted through that loop portion, away from the branch magneticcircuit including armature I0, and is hence not eifective to attract thearmature.

- Let us now consider the conditions which exist when the two front andback contacts of relay CF are permanently bridged, so that both windings3 and 4 are continuously energized. These windings then buck each otherin sending flux through the loop 2 and through the branch magneticcircuit including armature I0. Hence the flow of magnetic flux isreduced to a minimum and is not sufilcient to attract the armature I0.

From the foregoing, it may be seen that the relay I picks up thearmature I0 when and only when the code following relay CF is followingcode and its contacts are operating properly.

FIG. 2

This figure represents a side elevational view of the-relay I, which wasshown diagrammatically in Fig. 1. Most of the parts illustrated in Fig.2 are also illustrated in Fig. 1, and have been given the same referencecharacters.

Those parts will not be further described.

Referring to Fig. 2, it may be seen that the magnetic loop 2 is mountedon an insulated base plate I5, and that the pole structures 8 and 9 arealso mounted on the base plate I5 so as to project downwardly throughit. The armature I0 is hinged on nonmagnetic extensions of the portions8a and 9a of the pole structures. The base plate I5 carries threeterminal posts I6, I! and I8 which extend upwardly from its uppersurface and project downwardly through the base plate. Terminal post I6is connected by means of a detail connection IS with a movable contact2:! carried by the armature I0. Terminal post I! carries at its lowerend a front contact 2I which cooperates with the movable contact 28.Terminal I8 carries at its lower end a back contact 22 which cooperateswith the movable contact 20.

FIG3

There is shown in this figures. relay 23 which corresponds functionallyto the relay I of Figs. 1 and 2, but is somewhat different in form.Relay 23 includes a magnetic loop circuit 24 carrying two windings 25and 26 which correspond generally to the windings 3 and 4 of Fig. 1. Theenergizing circuits for windings 25 and 26 are not shown, and may beidentical with those shown for the windings 3 and 4 of Fig. 1.

One side 24a of the magnetic :loop 24 carries a shading coil or ring 21,which corresponds to the shading coil I of Fig.

The magnetic loop 24 is provided with a downward extension 24?)connected to the portion 24a at its upper end. The lower end ofextension 2 b is separated from a pole structure 28 .by an air gap 29.An armature 30 is pivotally mounted at one end near the lower end of theportion 24a of the magnetic loop 24, as on hinge 39a made of brass. Thefree end .of armature 3o extends adjacent the pole structure 28. Thepole structure 23 corresponds to the pole structures 8 and 9 of Fig. 1,and is provided with magnetically parallel portions 28a and 28b. Ashading ring 3|, corresponding to the shading ring is of Fig. 1, iscarried on the portion 28a of the pole structure 28. A nonmagnetic corepin 32 is provided to prevent direct engagement of armature 3G with thepole structure 28.

- The extension 2422, pole structure 28, and armature 35 form a branchmagnetic circuit which corresponds to the branch mag'netic circuit ofFig. 1, including pole structures 8 and 9 and armature I0. 1

The operation of the relay- 23 of Fig. 3 is analogous in every way tothat of the relay I of Figs. 1 and 2, and it is believed unnecessary todescribe it in detail. I a l Although I have herein shown and describedonly two forms of electric relays embodying my invention, it isunderstood that various changes and modifications may be made thereinwithin the scope of the appended claims without departing from thespirit and scope of my invention.

Having thus described my invention, What I claim is:

1. A code detecting relay comprising a magnetic circuit including aclose-d loop of magnetic material, two electric windings on said loop,means for alternately energizing said windings to create opposingmagnetic fluxes in said loop, a shading coil on said loop, and a branchmagnetic circuit forming a magnetic shunt around said shading coilduring transient magnetic conditions in said loop; said branch circuitincluding an armature and at least one pole structure toward which saidarmature is at times attracted; said branch circuit having an air gapbetween each pole structure and the closed loop so that its reluctanceis greater than that of the loop during steady magnetic conditions inthe loop; said shading coil and air gaps cooperating to retain saidarmature in its attracted position when and only when said windings arealternately energized at a frequency within a predetermined range.

2. A code detecting relay comprising a magnetic circuit including aclosed loop of magnetic material, two electric windings on said loop,means for alternately energizing said windings to create opposingmagnetic fluxes in said loop, a shading coil on said loop, and a branchmagnetic circuit forming a magnetic shunt around said shading coilduring transient magnetic conditions in said loop; said branch circuitincluding an armature and at least one pole structure toward which saidarmature is at times attracted; said branch circuit having an air gapbetween each pole structure and the closed loop so that its reluctanceis greater than that of the loop during steady magnetic conditions inthe loop; said pole structure comprising magnetically parallel portionsand a second shading coil on one of said portions, said second shadingcoil being effective to retain said armature in its attracted positionduring transient magnetic conditions in said branch magnetic circuit,said shading coils and said air gaps cooperating to retain said armaturein its attracted position when and only when said windings arealternately energized at a frequency Within a predetermined range.

3. A code detectin relay comprising a ma netic circuit including ahollow rectangular loop of magnetic material, two electric windings onopposite sides of said loop, means for alternately energizing saidwindings to create opposing magnetic fluxes in said loop, a shading coilon a third side of said loop, and a branch magnetic circuit forming amagnetic shunt around said shadin coil during transient magneticconditions in said loop, said branch circuit including an armature andtwo pole structures extending from the ends of said third side towardsaid armature and toward which said armature is at times attracted; saidbranch circuit having air gaps between said pole structures and the endsof said third side so that its reluctance is greater than that of theloop during steady magnetic conditions in the loop; each said polestructure comprising magnetically parallel portions and a second shadingcoil on one of said portions, said second shading coil being effectiveto retain said armature in its attracted position during transientmagnetic conditions in said branch magnetic circuit, said first shadingcoil and air gaps cooperating to retain said armature in its attractedposition when and only when said windings are alternately energized at afrequency within a predetermined range.

4. A code detecting relay comprising a magnetic circuit including ahollow rectangular loop of magnetic material, two electric windings onsaid loop, means for alternately energizing said windings to createopposing magnetic fluxes in said loop, a shading coil on one side ofsaid loop, and a branch magnetic circuit forming a magnetic shunt aroundsaid shading coil during transient magnetic conditions in said loop;said branch circuit including an armature pivotally mounted adjacent oneend of said one side and a pole structure extending from the other endof said one side toward said armature and toward which said armature isat times attracted; said branch circuit having an air gap between eachpole structure and the closed loop so that its reluctance is greaterthan that of the loop during steady magnetic conditions in the loop;said pole structure comprising magnetically parallel portions and asecond shading coil on one of said portions, said second shading coilbeing effective to retain said armature in its. attracted positionduring transient magnetic conditions in said branch magnetic circuit,said first shadin coil and air gaps cooperating to retain said armaturein its attracted position when and only when said windings arealternately energized at a frequency within a predetermined range.

ANDREW HUFNAGEL.

REFERENCES CITED The following references are of record in the

